Starting switch for electrical discharge lamps



1944. P. 1.. BETZ STARTING SWITCH FOR ELECTRICAL DISCHARGE LAMPS Filed Feb. 21. 1942 2 Sheets-Sheet 1 i 3 w M I 3 mi: m F n 1% 4 5% m 1 1.. 7 16 6 B/ m p w. M. Q @l i n mm w /& ro 9 1 we rt u 4x M Q E m/. m m Z W a, H m/ m m TM 2 we 3 W 3;

Aug. 29, 1944.

P. L. BETZ STARTING SWITCH FOR ELECTRICAL DISCHARGE LAMPS Filed Feb. 21, 1942 2 Sheets-Sheet 2 14/ I I I? ]3 6 |m=u'r I6 7 23 12 11 9 d6 F1Q.5

/g7 /93 awe/Mom 60 Patented Aug. 29, 1944 STARTING SWITCH FOR ELECTRICAL DISCHARGE LAMPS Paul L. Betz, Baltimore, Md., assignor to Consolidated Gas Electric Light and Power Company of Baltimore, Baltimore,

tion of Maryland Md., a corpora- Application February 21, 1942, Serial No. 431,894

7 Claims. (01. 315-100) This invention relates to starting switches for electrical discharge lamps, such as fluorescent lamps, and more particularly to starting switches which are so constructed that the starting operations of the switch are discontinued automaticallyif the lamp is defective or otherwise unable to maintain the electrical discharge.

Generally stated, an electrical discharge lamp comprises a pair of spaced electrodes in an envelope containing a gas or mixture of gases at a suitable pressure. The electrodes are adapted to be heated to incandescence by passage of an electric current therethrough, and are in circuit with a starting switch whose function is to momentarily connect said electrodes in series to bring them to incandescence and then interrupt the circuit through the electrodes, whereupon the resultant transient voltage, due to the presence of a reactor in another part of the circuit, initiates a discharge within the lamp.

As the lamp approaches the end of its useful life the decrease of electron emission from the electrodes makes the starting of the lamp more and more difficult, until a point is finally reached at which it is impossible to maintain the electrical discharge. Therefore, upon energizing the lamp, the starting switch continues to go through the cycle of starting operations above referred to, successively making and breaking the filamentheating circuit, and if the lamp fails to start, this continued operation of the starting switch may result in damage to the switch itself or to the transformer or to the reactor associated therewith.

It is an object of the present invention to provide an improved starting switch for electrical discharge lamps with means whereby, after a limited number of unsuccessful attempts to start a lamp, the starting operation is discontinued automatically.

A further object of the present invention is to provide a starting switch of the character referred to with means for discontinuing the starting operation of the switch under abnormal conditions and which, upon deenergization, is automatically restored to a condition for normal operation.

Another object of this invention is to provide an improved starting switch for electrical discharge lamps with safety means which discontinues the operation of the starting switch if, after a predetermined number of cycles, the lamp fails to start,

Another object of this invention is to provide a starting switch of the character referred to with a switch which is normally operative to maintain the desired operation of the starting circuit but which, under abnormal conditions, is electrically operated to interrupt the starting circuit.

Another object of this invention is to provide a starting switch for electrical discharge lamps which fulfills the foregoing objects and which at the same time is of such simplicity that it may be readily embodied in commercial starting switches for electrical discharge lamps without unduly complicating the circuit arrangements or the associated structure.

Other objects of the invention will appear as the description of the invention proceeds.

The present invention may be applied to lamp starters of types now available commercially, such as the type which employs spaced bimetallic contact members enclosed in an envelope filled with a gas or mixture of gases at reduced pressure so that a glow discharge may be initiated between these members to initiate the starting operation of the lamp, and the type employing bimetallic contact members that are actuated by heat evolved in a heating unit, the position of the contacts being governed by the rate of of heat in the said unit.

The invention is capable of receiving a variety of expressions, several of which are illustrated on the accompanying drawings to show embodiments of the present invention in starting switches of types which are now commercially available as above referred to, but it is to be expressly understood that the drawings are for purposes of illustration only and are not intended to be a definition of the limits of the invention, reference being had to the appended claims for that purpose.

Referring in detail to the drawings, wherein the same reference characters are employed to designate corresponding parts in the several figures, each of Figs. 1, 2, 3, 4 and 5 respectively illustrates diagrammatically a circuit arrangement for a starting switch for electrical discharge lamps embodying the present invention. In the form shown in Fig. 1, an electrical discharge lamp, as a fluorescent lamp, is diagrammatic'ally illustrated at ill, the same having filamentary electrodes H and I2 respectively connected through wires l3 and M to the terminals of a transformer 15 having an input represented by the leads Hi. In series with the transformer l5 and the electrodes II and I2 is a suitable reactor for initiating the discharge in the lamp in accordance with principles well understood in the art." The electrodes H and 12 are also in dissipation series through wires I 6 and I9, respectively, with the terminals 20 and 2| of the starting switch now to be described.

The improved starting switch embodying the present invention is connected with said terminals 2n and z and m the embodiment of Fig. 1 employs the glow type starter switch indicated at 22, the same having spaced bimetallic contact arms 23 and 24 which are respectively provided with contacts 25 and 26. If desired, only one of contact arms 23, 24 need be made of thermostatic bimetal. Starter switch 22 has leads 30 and 3|, and a condenser 21 is connected in parallel with the said starter switch 22 by wires'28 and 29 and by wire 32, said condenser absorbing the energy incident to the separation of the contacts 25 and 26 as understood in the art.

Connected in series with the aforesaid parallel circuits including the glow type starter switch 22 and the condenser 21, by wires 33 and 34, is a normally closed switch composed of spaced bimetallic contact arms 35 and 36 provided respectively with contacts 31 and 36, one of which, as contact 31, is mounted on its bimetallic contact arm by means of an interposed spring 39. Contact arm 36 is connected to the terminal 20 by wires 40 and 4|. Associated with the bimetallic contact arm 36 are resistors 42 and 43 in series, said resistors constituting heating elements in heat interchanging relationship with said arm 36. From a point intermediate said heaters 42 and 43 a wire 44 leads to the wire 33, while the opposite end of heater 43 is connected to wire 4| by wire.45 and the opposite end of heater 42 is connected to wire 29 by wire 46, wire 29 in turn being connected'to terminal 2| by wire 41. v On energizing transformer current flows in the circuit includingwire |4,' electrode 2, wire l9, terminal 2|, wires 41, 29 and. 30, bimetallic contact arm 23, and thence as a glow discharge through the gas in the starter switch 22 to bimetallic contact arm 24 whose contact 26 is normally separated from contact 25 on arm 23, then from contactarm 24 through wires 3|, 33 and 34, bimetallic contact arm 35, spring 39, contacts 31 and 38, bimetallic contact arm 36, wires 46 and 4|, terminal 29, wire I 8, electrode wire I3 and reactor l1 to the other side of the transformer l5. The glow discharge be.- tween the bimetallic arms 23 and 24 causes heating of the said arms with their consequent deflection toward each other to close the circuit by engagement of the contacts 25 and 26, and thereupon current for heating the electrodes to incandescence flows through said electrodes II and I2 of the lamp II]. On closure of the contacts 25 and 26 the glow discharge between arms 23 and 24 in the starter switch 22 ceases, with a consequent cooling of arms 23 and 24. Said contacts 25 and 26 are thereupon separated by the flexure of said arms 23 and 24 away from each other as a result of the cooling of said arms, and this interruption of the electrode heating'current causes a high transient voltage to be applied between the electrodes H and i2. If the lamp I0 is operative and can maintain an electrical discharge, such discharge will be established, and when present the voltage drop across the discharge may be of the order of one half the voltage appearing across the electrodes when no discharge is present. This voltage drop between the electrodes and I2 is applied to the starting switch both through wire 4|, heater 43 and wire, and through wire 40, bimetallic contact arms 36 and 35 with their contacts 36 and 31 and wire 34, but as the contacts 31 and 38 are normally in engagement the circuit through the heater 43 is short-circuited by the circuit through the bimetallic contact arms 35 and 36. When-lamp I9 is operating normally the low voltage drop between the electrodes and I2 applied to the heater 42 causes only a low energy dissipation in said heater and a corresponding small deflection of bimetallic contact arm 36 under the influence of the heat so generated. Owing to the presence of the spring 39, which isnormally under tension when the bimetallic contact arms 35 and 36 are in their normal position, spring 39 may expand sufficiently to cause contacts 31 and 36 to remain in engagement with each other during such small deflection of bimetallic contact arm 36 as is caused by heater 42 when the lamp I6 is operating normally.

Should lamp l0 be defective such that a discharge is not maintained between the electrodes II and I2, the glow starter switch 22 will repeat its cycle of closing and opening its contacts 25,

.26 in a new eflort to start the lamp. At each failure of the lamp It to establish a discharge, approximately full voltage is applied to heater 42, and after repeated starting attempts of said glow starter switch 22 suiiicient heat is generated by heater 42 under the aforesaid repeated applications of full voltage thereto to-cause bimetallic contact arm 36 to flex away from bimetallic contact arm 35 to a point where spring 39 cannot cause contact 31 to follow contact 38. Thereby the circuit through the switch 35, 36 is interrupted. When this occurs both heaters 42 and 43 are energized but the voltage applied to the glow starter switch 22 is now governed by the resistance relationship between said heaters 42 and.43. The voltage across lamp H) is now applied to heaters 42 and 43 in series by the circuit including terminal 2|, wires 41, 29, 46, heaters 42, 43, wires 45, 4| to terminal 20, and the voltage drop across heater 42 is applied to glow starter switch 22 by wires 46, 30, and wires 44, 33, 3|. Preferably the heaters 42 and 43 are of approximately the same resistance value so that approximately one half of the voltage is applied across the glow starter switch 22, a voltage which i insuflicient to cause said glow starter switch 22 to form a glow discharge and reinitiate a starting operation. Therefore the opening of the contacts 31 and 38 results in discontinuing the flow of current through the electrodes II and I2 except for such current as may now flow through the resistors 42, 43. The energy dissipated in resistors 42, 43 under theseconditions, however, i suiflcient to maintain bimetallic contact arm 36 flexed sufiiciently to hold contact 38 out of engagement with contact 31. Hence further attempts to start lamp H! are discontinued.

The starter switch including its associated circuits may be restored to normal operation by deenergizing the transformer 5, by removing the lamp It or by disconnecting the starter at its terminals 26 and 2 I, because such interruption of the current flow through heaters 42, 43 permits bimetallic contact arm 36 to cool, whereupon the parts are restored to the relationship illustrated on the drawings, reestablishing the circuit through bimetallic contact arms 35 and 36 and their contacts 31 and 38.

Bimetallic contact arm 35 functions to compensate for variations of temperature in' the ambient. As increase of temperature in the ambient would tend to cause bimetallic contact arm 36 to flex so as to disengage contacts 31 and 38 irrespective of the operation of the heaters 43 and 42, bimetallic contact arm 35 is so constructed as to respond to the ambient temperature, maintaining contacts 31 and 38 in engagement independent of fluctuations in the ambient temperature, and thereby rendering movements of bimetallic contact arm 36 with respect to contact arm 35 dependent only on heat derived from the heaters 43 and 42.

The circuit indicated diagrammatically in Fig,

2 is similar to that of Fig. 1, like reference characters being used to indicate like parts, but in this embodiment the heaters 42 and 43 are replaced by a single resistor. The embodiment of Fig. 1 would be identical with that of Fig. 2 in an electrical sense if the heater 42 were shortcircuited and wire 44 were removed. In this embodiment the single resistor 48 is connected by wires 49 and 58 to the wires ly. When the discharge is maintained across the electrodes I and I2 the rate of energy dissipation of resistor 48, which constitutes a, heater in heat interchanging relationship with the bimetallic contact arm 36, is low, but when the discharge cannot be maintained between said electrodes the dissipation of heat at resistor 48 is high. Following repeated attempts to start a defective lamp, as above explained in conjunction with the embodiment of Fig. l, the heat evolved at heater 48 causes the circuit to .be interrupted at contacts 31 and 38, whereupon the electrode heating circuit is interrupted and further operation of the glow starter switch 22 is discontinued. In the normal operation of the lamp, however, the low heat dissipation of resistor 48 causes only slight movement of bimetallic contact arm 36, and the circuit is not interrupted between contacts 31, 38 because of the follow-up action of the spring 39 as above explained. As in the embodiment of Fig. 1, the starter of Fig. 2 is restored to normal operation by deenergizing the starter for a long enough period to permit bimetallic arm 36 to cool, whereupon the electrical circuit through contacts 31 and 38 is reestablished.

In the embodiment of Fig. 3 the present invention is applied to a commercial type of starting switch which employs thermal means for operating the switch. In this embodiment abimetallic contact arm is provided with contacts 52 and 53. Co-operating with contact 52 is contact 54 carried by arm 55. Co-operating with contact 53 is contact 56 carried by arm 51. Arms 55 and 51 are spaced with respect to each other but moved as a unit by bimetallic arm 58 on which said arms 55 and 51 are mounted. As shown, a resistor 59 is interposed between the arm 51 and the arm 58 but if preferred contact 56 may be made of a material having a relatively high resistance so as to make the use of a separate resistor at 59 unnecessary.

Associated with bimetallic contact arm 5| is a resistor 68 constituting a heater in heat interchanging relationship with said contact arm 5|. When the circuit is not energized, arm 5| holds contact 53 in engagement with contact 56, but under the influence of heat generated byresistor 68, arm 5| flexes to the left as viewed in the drawings so as to withdraw contact 53 from contact 56 and engage contact 52 with-contact 54. Connected in series with the bimetallic contact arm 5| and the terminal 28, by wires 6| and 62 respectively, is a thermally operated switch composed of bimetallic contact arms 63 and 64 respectively provided with contacts 65 and 66 one of which, as contact 66, is mounted on its bimetallic con tact arm by a spring 61 which is held under tension when the bimetallic contact arms 63 and. 64 are unflexed. Heater 68 is also in heat interchanging relationship with the bimetallic contact arm 63 and is connected in shunt to the switches 63, 64 and 5|, 58 by wires 68 and 69. Bimetallic contact arm 58 is connected to wire 69 by wire 18, wire 69 being connected to terminal 2| by wire 41.

Upon energizing transformer |5 in the embodiment of Fig. 3, current flows through the circuit including the reactor l1, electrode ter- 4| and 29, respectiveminal 28, wire 62, bimetallic arm 64, spring 61, contacts 66 and 65, bimetallic arm 63, wire 6|, bimetallic arm 5|, contacts 53 and 56, arm 51, resistor 59, bimetallic arm 58, wires 18, 69 and 41, terminal 2| andelectrode l2 back to the other side of transformer |5. This current raises the temperature of the electrodes II and I2 to incandescence. Current also flows in the circuit which comprises wire 68, heater 68 and wire 69. The voltage applied to heater 68 is the voltage applied across electrodes II and I2, and if a discharge is established and maintained between said electrodes II and I2 the voltage drop therebetween is on the order of one half the voltage which exists across these electrodes when the discharge is not present. Hence the energy dissipated in heater 68 is less when the discharge is present between electrodes \and I2 than when no discharge is present.

When heating current flows through the electrodes H and I2, the energy dissipated in heater 68 causes bimetallic arm 5| to flex toward the left as viewed in the drawings to. separate the contacts 53 and 56. Thereupon a high transient voltage is applied between the electrodes H and I2 due to the action of the reactor H in a manner well understood in the art. If the lamp I8 is operative this transient voltage initiates the electrical discharge between the electrodes II and I2 and the lamp continues in operation. Under operating conditions, the low energy dissipation of heater 68 causes bimetallic arm 5| to assume a position such that the electrical circuit is open between the contacts 53 and 56 with the arm 5| not flexed sufliciently to engage contacts 52 and 54. Also, this low energy dissipation of heat from resistor 68 causes bimetallic arm 63 to deflect a small amount toward the left as viewed in the drawings, but this flexure is not sufficient to separate contacts and 66 owing to the follow-up action of the tensioned spring 61 as above explained in conjunction with the embodiment of Figs. 1 and 2. I

If lamp |8 is defective, however, or for any reason fails to maintain the electrical discharge between the electrodes II and I2, full voltage is thenapplied to the heater 68 and the increased heat dissipation therefrom causes bimetallic arm 5| to flex still further to the left as viewed in the the circuit between the contacts 52 and 54. Thereupon the flow of heating current through the electrodes H and I2 is established by the circuit which includes wire 6|, bimetallic arm 5|, contacts 52 and 54, arm 55, bimetallic arm 58 and wire 18. Upon closure of the contacts 52 and 54 a shunt is established across the circuit which includesthe heater 68, thereby permitting heater 68 to cool, whereupon bimetallic arm 5| cools and breaks the circuit at contacts 52 and 54. Thereby another high transient voltage is H and |2.

initiated between the electrodes If again a discharge between said electrodes is not established, heater 68 again dissipates energy at its maximum rate and bimetallic arm 5| repeats the action above outlined.

After a limited number of repetitions of the cycle as Just described, the increased heat dissipation of heater 68 causes arm 83 to deflect beyond the position in which the spring 51 may hold the contacts 85 and 8 6 in engagement, thereby separating these contacts to interrupt the electrode heating circuit of the lamp except through heater 88. However, the current flowing through the heater 88 is insufficient to cause incandescence of the electrodes II and I2, while the amount of energy dissipated at heater 88 is suflicient to hold bimetallic arm 53 in its flexed position wherein the contacts 65 and 86 are out of engagement. Therefore due to this interruption in the circuit through the starting switch 5|58 further attempts of the latter to start the lamp are discontinued.

Bimetallic contact arm 84 operates to compensate for the ambient temperature as above explained in conjunction with the operation of bimetallic contact arm 35 with respect to its associated arm 36, and bimetallic arm 58 also functions in conjunction with bimetallic contact arm 5| to compensate for fluctuations in the ambient temperature, arm 58 moving arms 55 and 51 and .their associated contacts 54 and 58 in the same direction and to the same amount that bimetallic contact arm 5| moves its contacts 52 and 53 in response to changes in the ambient as distinguished from the efiect of heat generated in the reactor 88.

As in the embodiments above described, to restore the starter to its normal operation, it is only necessary to deenergize the starter by interrupting the circuit at the transformer or the lamp or the terminals, whereupon bimetallic contact arm 63 cools to reestablish the circuit through contacts 65 and 86, while bimetallic contact arm 5| cools and returns to the position illustrated in Fig. 3.

In each of the embodiments so far described the contacts which are separated by the action of electrical means rendered effective when the lamp fails to start have been made separate from the contacts in the starter switch proper that function in initiating the discharge in the lamp. However, the present invention may be embodied in structures wherein the electrical means cooperates with the same set of contacts which function during normal operation of the lamp for the purpose of so acting on said contacts as to discontinue their capacity to co-operate and repeat starting cycles after a limited or predetermined-number of cycles in which the lamps fail to start. Circuits embodying the invention as just referred to are illustrated in Figs. 4 and 5.

In the form shown in Fig. 4, the starting switch proper is similar to that illustrated in Fig. 3 and includes the bimetallic contact arm 18 connected by wire 88 to the terminal 28, said arm 18 being provided with contacts 1| and 12 adapted to cooperate with contacts 13 and 14 respectively. Contact 14 is mounted on arm 15 which may include a resistor 16 as described in conjunction with the embodiment of Fig. 3, or as there described, contact 14 may be made of resistant material so thatthe provision of a separate resistor 18 is unnecessary. Contact 13 is mounted on a bimetallic contact arm 11, and said arms 15 and 11 are mounted to move as a unit on bimetallic arm 18 connected by wire 19 and wire 88 to the terminal 2|. Co-operating with bimetallic contact arm 18 is a resistor 8| in heat interchanging relationship with said arm 18, and connected in series with said heater 8| is a second resistor 82 constituting a heater in interchanging relationship with the bimetallic contact arm 11, said heaters 8| and 82 being connected in shunt, by wires 83 and 84, around the circuit through the switch proper constituted by elements 18 to 18, but being in series with the electrodes II and I2 through wire I8, terminal 28, wire 88, wire 83, heaters 8| and 82, wire 84, wire 88, terminal 2| and wire I9. As in the other embodiments a condenser 21 is connected in parallel with the circuit through the switch proper, composed of elements 18 to 18, by wires 8| and 82.

In operation the rate of energydissipation in 4 resistors 8| and 82 depends upon whether or not a discharge exists between electrodes II and II, the dissipation being greater when no discharge is present as above explained. When the lamp starts normally and continues in normal operation the rate of dissipation of energy at heater 8| is relatively low. This heat causes bimetallic contact arm 18 to flex to the left as viewed in w the drawings, breaking the circuit at normally closed contacts 12 and 14, but not engaging contacts 1| and 13, said arm 18 assuming an intermediate position of equilibrium which maintains the circuit open at both of said pairs of contacts. The low rate of energy dissipation in resistor 82 also causes bimetallic contact arm 11 to flex so as to increase the spacing between contacts 1| and 13 slightly more than would exist if arm 11 were not temperature responsive. If the lamp fails to start, application of the higher voltage to resistors 8| and 82 causes arm 18 to flex further to the left as viewed in Fig. 4, engaging contacts 1| and 13. This establishment of the circuit from arm 18 through contacts 1| and 13, arm 11, arm 18 and wire 18 reduces the heat dissipation at heaters 8| and 82 and arm 18 cools sufliciently to flex its contact 1| away from contact 13, thereby applying a high transient voltage across the electrodes II and I2 as above explained. During this operation of the starter switch the heat dissipation at resistor 82 tends to flex arm 11 further to the left as viewed in no longer co-operate with contact 1| notwithstanding that heater 8| is also dissipating energy to hold arm 18 in-its extreme left-hand position. Thereby the electrode heating current of the lamp can not be established and further at-- tempts to start the lamp are discontinued.

As in other embodiments the starter may be reset for normal operation by merely deenergizing the starter at the transformer, the lamp or the terminals for a suflicient period to permit cooling of the bimetallic contact arms 11 and 18, whereupon the parts are restored to the relative position illustrated in Fig. 4.

.The embodiment of Fig. 5 is in many respects similar to that of Fig. 4, corresponding parts being indicated by the same reference characters, except that contact 14 is mounted on a bimetallic contact arm 85 which includes a resistor 16 in circuit therewith, although as above explained, the contact 14 may be made of-resistant material so as to make the use of a separate resistor unnecessary, while the bimetallic contact arm 18 is omitted and arms 1'! and 85 are connected to the wire 19 by wires 86 and 81 respectively.

In the embodiment of Fig. 4 bimetallic contact arm 78 serves to compensate for variations in ambient temperature, moving arms 11 and 15 as a unit as above explained in conjunction with the embodiment of Fig. 3. In the embodiment of Fig. 5, on the other hand, bimetallic contact arm 85 responds to ambient temperature as well as do arms and TI, and hence insofar as variations of ambient temperature are concerned all of said arms flex together to compensate for changes in the temperature of the ambient while relative movement between said arms is due solely to the action of heaters 8| and 82 on arms 10 and 11, respectively.

It will therefore be perceived that the present invention provides means for discontinuing the operation of the starting switch of an electrical discharge lamp if the lamp be defective or otherwise fails to start. Said means for discontinuing the operation of the starting switch operates automatically, and by properly constructing the bimetallic arms and by properly constructing and associating with said arms the heater elements described, it is possible to nicely predetermine the number of applications of transient voltage to the lamp in before the starting switch is rendered inoperative. It will further be perceived that the means provided for discontinuing the operation of the starting switch has the advantage that it is automatically reset for its normal operating condition upon deenergization of the switch as by interrupting the current supply to the lamp or removing the lamp from the circuit or disconnecting the switch. Furthermore, the invention provides a relatively simple means for eiTecting the foregoing automatic operations and one that may be associated with lamps employing various forms of starting switches and without unduly complicatingthe circuits or the structures involved. In each of the embodiments disclosed normally co-operating contacts function during the normal operation of the circuit to provide means to assure a predetermined limited number of starting cycles that shall be applied to the lamp if the lamp fails to start upon the first application of the starting voltage thereto, while electrical means rendered efiective by the voltage existing as a result of the failures of the lamp to start causes said contacts to assume a relationship in which they can no longer co-operate to produce further starting cycles of the switch. Thereby the danger of injury to the starting switch and its transformer, reactor and associated parts by continuing operation of the starting switch when the lamp fails to start has been eliminated in a simple and efiicient way that may be readily embodied in commercial starting switches of various kinds now to be found on the market as well as embodied in new switch constructions.

While the embodiments of the invention illustrated on the drawings have been described with considerable particularity, it is to be expressly understood that the invention is not limited thereto as other circuit arrangements, other forms of starting switch, other electrical means energized by the failure of the lamp to start to move normally cooperating contacts into relatively inoperative relationship, etc., will now readily suggest themselves to those skilled in the art without departing from the principles of this inodically opening and closing said circuit, said starting circuit also including normally closed contacts, a bimetallic arm on which one of said contacts is mounted, and a heater associated with said arm and connected in' parallel with said electrodes, said heater having a low or high voltage applied thereto dependent upon whether a discharge is or is not established through said lamp, repeated applications of high voltage to' said heater causing said bimetallic arm to flex and move its'associated contact to open position and retain the samein said position and said arm restoring said contacts to closed position only upon deenergizing said lamp.

2. In a starting device for electrical discharge lamps of the type having at least two electrodes, one at least of said electrodes being of the filamentary type and requiring an electrode heating current only during starting, in combination with a starting circuit, including the electrodes of said lamp and contact-means for periodically opening and closing said circuit, said starting circuit also including a pair of normally closed contacts, a bimetallic arm on which one of said contacts is mounted, a heater connected in parallel with said electrodes and in heat interchanging relationship with said bimetallic arm, said heater constructed to dissipate different amounts of energy dependent upon I whether or not the discharge is maintained in said lamp, to flex said bimetallic arm insufiiciently to interrupt the circuit at said normally closed contacts under the heat, dissipation existing when the discharge through the lamp is maintained and to flex said bimetallic arm after a plurality of operations of said first named contact means to move its associated contact into open position under the heat dissipation existing when the discharge through the lamp is not maintained, said bimetallic arm flexing sufliciently upon deenergizing said lamp following unsuccessful at tempts to start said lamp to restore said normally closed contacts to closed position.

3. .In a starting switch for electrical discharge lamps of the type having at least two electrodes, one at least of said electrodes being of the filamentary type and requiring an electrode heating current only during starting, in combination with a starting circuit including the electrodes of said lamp, a glow discharge starter switch for periodically opening and closing said starting circuit and additionally normally closed contacts in circuit therewith, a bimetallic arm on which one of said contacts is mounted, and a heater associated with said bimetallic arm and in shunt with said switch and with said contacts and actuated by a predetermined period of repeat ed failure of said lamp to start for flexing said bimetallic arm to move said contacts to and I retain the same in open position as long as said lamp is energized, said arm operating to close,

/ said secondnamed contacts only upon deenergizone at least of said electrodes being of the filamentary type and requiring an electrode heating current only during starting, in combination with a starting circuit including the electrodes of said lamp and thermally operated means for periodically opening and closing said circuit to initiate the operation of said lamp, said circuit including normally closed contacts, a bimetallic arm on which one of said contacts is mounted, and a heater associated with said bimetallic arm and in shunt with said first named means and with said contacts and actuated only after a predetermined period of repeated failure of said lamp to start to flex said bimetallic arm to move said contacts to open position, said arm operating to close said contacts upon deenergizing said lamp.

5. In a starting switch for electrical discharge lamps of the type having at least two electrodes, one at least of said electrodes being of the filamentary type and requiring an electrode heating current only during starting, in combination with a starting circuit including the electrodes of said lamp and a starting switch for initiating the operation of said lamp and applying a plurality of starting impulses thereto if the lamp fails to start the first time, means for discontinuing the operation of said starting switch after a predetermined period of failure of the lamp to start, said last named means including an additional pair of normally closed contacts in circuit with said starting switch and electrodes, a bimetallic arm on which one of said contacts is mounted,,

and a heater connected in parallel with said electrodes and energized by the voltage arising only after a predetermined period of repeated failure of said lamp to start to flex said bimetallic arm and move its associated contacts relatively out of co-operative relationship and for restoring said co-operative relationship upon deenergization of said lamp, said contacts having means co-operating therewith for maintaining the same in engagement during the fiexure of said arm arising from the energy dissipated from said heater under the voltage applied thereto during normal operation of the lamp.

6. In a starting switch for electrical discharge lamps of the type having at least two electrodes,

one at least of said electrodes being of the filamentary type and requiring an electrode heating current only during starting, in combination with a starting circuit including the electrodes of said lamp and a starting switch ior initiating the operation of said lamp and applying a plurality of starting impulses thereto if the lamp fails to start the first time, means for discontinuing the operation of said starting switch after a predetermined period of failure of the lamp to start, said means including a pair of contacts in circuit with said starting switch and electrodes, a circuit in parallel with said electrodes, said parallel circuit including a heater, and meansresponsive to said heater for opening and retaining open said last named contacts upon continued dissipation 01' energy from said heater following failure 01 said lamp to start and for closing said last named contacts upon deenergizing said heater.

7. In a starting switch for electrical discharge lamps of the type having at least two electrodes, one at least of said electrodes being of the filamentary type and requiring an electrode heating current only during starting, in combination with a starting circuit including the electrodes of said lamp and a starting switch for initiating the operation of said lamp and applying a plurality of starting impulses thereto if the lamp fails to start the first time, means for discontinuing the operation of said starting switch alter a predetermined period of failure of the lamp to start, said means including a pair of contacts in circuit with said starting switch and electrodes, a circuit in parallel with said electrodes, said parallel circuit including a heater, and means responsive to said heater for opening and retaining open said last named contacts upon continued dissipation of energy from said heater arising from failure of said lamp to start and for closing said last named contacts upon deenergizing said heater, said contacts having means for maintaining the same in engagement under the heat dissipation from said heater during normal operation of said lamp.

PAUL L. BETZ. 

